Comparing the USU and Key/BYU election prediction polls

Both polls agree that Republicans will sweep Utah’s statewide races decisively.

We saw something unusual this week: Two well-designed polls, conducted independently (not by campaigns), in the field at the same time. Damon Cann published the USU pre-election poll last Wednesday, and Quin Monson published the Key Research/BYU election prediction poll yesterday.

Both polls covered the major statewide races. My first instinct was to compare the results. For those with the same instincts, I thought I’d put up the comparison here. Both polls agree that Republicans will sweep Utah’s statewide races decisively.

Both polls drew their sample from the state’s list of registered voters. Both were in the field at the same time. USU was in the field October 8-13, while Key Research was in the field October 9-13. USU sampled 206 voters. Key Research sampled 500. These sample sizes produce margins of error of 7.6% (USU) and 4.4% (Key/BYU). Here’s the predictions in a single table:

USU Key/BYU
President Romney by 53% Romney by 51%
US Senate Hatch by 44% Hatch by 39%
Governor Herbert by 59% Herbert by 46%

The 2 percentage point difference in the president race is negligible and well within the margin of error. The same of true of the 5 point difference in the US Senate race.

The 13 point difference in the gubernatorial race is large and outside the margin of error, although both polls predict a disappointing day for Peter Cooke. Of course, if you read Quin’s analysis, you’ll see that he makes some assumptions about undecided voters to predict that the actual result of the Herbert-Cooke showdown will come closer to a 53% margin, which comes closer to the USU prediction.

Wrapping up: Both polls generally agree. Assuming they correctly predict the actual results on election day, their agreement validates the polling methods so widely used by political scientists.

The USU poll included only statewide races, so we don’t have a comparison point for the Key/BYU poll’s predictions about the various US House races. Still, the agreement between the polls on the statewide races strengthens the credibility of the Key/BYU poll’s predictions within the House districts.

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About Adam Brown

Adam Brown is an assistant professor of political science at Brigham Young University and a research fellow with the Center for the Study of Elections and Democracy. You can learn more about him at his website.
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